The present invention relates generally to broadband multimedia data distribution systems, and more particularly, to apparatus for integrating satellite broadband data distributed over a cable TV network with legacy corporate local area networks.
Legacy corporate local area networks (LANs) can become congested under user demand for broadband multimedia data and other data services. These legacy networks are costly to replace or upgrade to meet the increasing demand for multimedia data. It would be desirable to have the ability to expand existing legacy network capabilities and avoid replacement or upgrade costs.
Currently available technology relating to the present invention includes a Multimedia Cable Networking Standards (MCNS) compliant "data over cable TV" architecture. By way of background, the Institute of Electronic and Electrical Engineering's (IEEE) 802.14 Cable TV Media Access Control and Physical Protocol Working Group was formed in 1994 to develop international standards for data communications over cable. The goal was to submit a cable modem Media Access Control and Physical Protocol standard to the IEEE in December 1995, but the delivery date slipped to late 1997.
Because of the delay in finalizing the IEEE 802.14 standard, certain cable operators, operating under a limited partnership dubbed Multimedia Cable Network System Partners Ltd. (MCNS), proceeded to research and publish their own set of interface specifications for high-speed cable data services. MCNS released its Data Over Cable System Interface Specification (DOCSIS) for cable modem products to vendors in March 1997. Many vendors have announced plans to build products based on the MCNS DOCSIS standard.
The differing cable modem specifications advocated by IEEE 802.14 and MCNS reflect the priorities of each organization. The 802.14 group focused on creating a future-proof standard based on industrial-strength technology. The members of MCNS, on the other hand, were concerned with mnimizing product costs and time to market. To achieve its objectives, MCNS sought to minimize technical complexity and develop a technology solution that was adequate for its members' needs.
At the physical layer, which defines modulation formats for digital signals, the IEEE and MCNS specifications are similar. The 802.14 specification supports the International Telecommunications Union's (ITU) J.83 Annex A, B and C standards for 64/256 QAM modulation, providing a maximum 36 Mbps of downstream throughput per 6 MHz television channel. The Annex A implementation of 64/256 QAM is the European DVB/DAVIC standard, Annex B is the North American standard supported by MCNS, while Annex C is the Japanese specification. The proposed 802.14 upstream modulation standard is based on QPSK (quadrature phase shift keying) and 16QAM, virtually the same as MCNS.
As for media access control, which sets the rules for network access by users, 802.14 specified Asynchronous Transfer Mode (ATM) as its default solution from the headend to the cable modem. MCNS uses a scheme based on variable-length packets that favors delivery of Internet Protocol (IP) data. Although the MCNS media access control is based on packets and the IEEE specifies fixed ATM cells, both cable modem solutions specify a 10 Base-T Ethernet connection from the cable modem to the PC.
It would be desirable to have a multimedia data distribution system and method that overcomes limitations of the Multimedia Cable Networking Standards architecture. Accordingly, it is an objective of the present invention to provide for broadband multimedia data distribution system apparatus for integrating satellite broadband data distributed over a cable TV network with legacy corporate local area networks.